The government's hopes to pass the bill, which is expected to provide cheap staple food to two-thirds of the nation's population, in the lower house on August 20 were belied as the Congress managers failed to gauge the Opposition strategy.

However, Sonia Gandhi, while launching the ambitious food scheme in Delhi, described it as "unparalleled in the world". Delhi was the first to roll it out after the government got the president to approve an ordinance in June.

"We have people who still don't get food and there are children who are malnourished. We decided to bring this scheme so that every poor gets food and no child sleeps without food," Sonia Gandhi said at Talkatora Stadium, not far from parliament.

"The guarantee of food provided by food security scheme on such a large scale is unparalleled in the world," she said.

The Bharatiya Janata Party (BJP) did not let the Lok Sabha function over its demand for the prime minister's statement as it was dissatisfied over the statement of Coal Minister Sriprakash Jaiswal made in the Rajya Sabha over the missing files on an issue that is being probed by the Central Bureau of Investigation (CBI) for alleged irregularities.

UPA chief Sonia Gandhi presents a recipient with an ceremonial oversized food card as Delhi CM Sheila Dixit looks on during the launch of the food security programme in New Delhi. AFP photo

The "missing files" pertain to decisions taken at various levels in the coal ministry and the government screening committees that decided on the controversial coal block allocations where the opposition alleges large-scale corruption at ministerial levels.

Raising the issue in the Lok Sabha, leader of Opposition Sushma Swaraj said the Prime Minister had taken "full responsibility" for the decisions of the coal ministry in a statement he made in the House on August 27 last year.

Amid cries of "shame-shame", Swaraj said the files included applications for coal blocks and alleged that they have gone missing as some big shots of the Congress were involved. She wanted the Speaker to direct the Prime Minister to make a statement. Singh had held the coal portfolio from 2006 to 2009 when the coal blocks were allocated.

The Rajya Sabha also witnessed uproar after which Jaiswal made a statement saying that a committee has been constituted to go into the issue of missing files which has held two meetings. "I would like to assure the House that my ministry would leave no stone unturned in tracing and providing the documents sought by the CBI," he said.

Though the BJP did not say it was opposed to the bill, party spokesperson Prakash Javadekar said they will not give up the demand for the prime minister's statement on the "missing files".

"We want the government to pass our amendments to the food security bill," he said, regarding the BJP's support to the government's flagship legislation.

Congress managers hoped the bill will be passed in the current parliament session, saying there still were three working days left in the week and four in the next.

"We will be trying our level best to get the food bill passed. We are talking to everybody (all political parties)," minister of state for parliamentary affairs Rajeev Shukla told reporters.

Parliamentary affairs minister Kamal Nath said: "We will use all rules to ensure that the house runs."

Food minister KV Thomas said he was confident of getting the legislation passed. "It is a very important bill."

However, with the government seemingly in no mood to succumb to the opposition's pressure tactics and allow a statement by the prime minister on the coal blocks files, the stage is set for a possible confrontation when the house meets Thursday after Raksha Bandhan holiday Wednesday.

While Sonia Gandhi launched the food security scheme at a function in Delhi, party Congress managers said if the opposition deliberately blocks the food bill, they will go directly to the people and explain things to them as to who had opposed this legislation.

Both the Samajwadi Party and the Bahujan Samaj Party (BSP) support the bill.

BSP supremo Mayawati said: "We support the bill as it is for the poor, but we want certain changes for which we will move amendments."

The Food Security Bill, expected to be a game-changer for the ruling Congress ahead of five assembly polls this year-end and the 2014 general elections, aims to provide subsidised foodgrain at prices much below the market rate to around 67% of India's 1.2 billion people. The bill is expected to benefit about 800 million people.

The bill, which is part of the Congress manifesto for the 2009 polls, will bring electoral benefits, the party is hoping just as the rural job plan, the Mahatma Gandhi National Rural Employment Guarantee Scheme, is credited with swinging the party's victory in the 2009 polls.

The bill will cost the government around Rs. 124,723 crore, the Congress has said. The bill was first introduced in parliament in December 2011. It remained with a standing committee for a year, before it was taken to the Lok Sabha for consideration and passing in the budget session that ended May 8.